Various forms of suspension systems have been developed for use on bicycle and motorcycles. The most common form is a front fork utilizing two telescoping assemblies positioned on either side of the front wheel. Front suspension is beneficial to the rider because it can improve handling and control as the suspension helps the front wheel follow the ground and provides isolation from the irregularities of the terrain. Typically the two telescoping assemblies are comprised of round inner and outer tubes in communication with one another through round cross section bushings. The inner tubes may be either the upper set of tubes, the stanchions, or the lower set of tubes, the sliders, depending on the design and application. In either case, the upper end of the stanchions is connected to one, or two fork crowns. Typically a bicycle has one fork crown below the head tube of the vehicle frame and a motorcycle will have a fork crown below and a fork crown above the head tube of the vehicle frame. A steer tube is connected to the crown that is below the head tube of the frame and extends up and through the head tube. The steer tube is supported at the bottom of the head and at the top of the head tube with bearings whose internal diameter is slightly larger than the outside diameter of the steer tube and whose outside diameter is a press fit into prepared features in the top and bottom of the head tube. The top of the steer tube is connected to the handlebar assembly of the  vehicle directly on a bicycle. On a motorcycle the top of the steer tube typically is mounted to the upper fork crown, which comprises part of the handlebar assembly. The stanchions extend from the lower fork crown down towards the ground and terminate a distance below the fork crown and above the front axle of the fork. The sliders provide front wheel axle mounting at their lower ends and extend upwards from the axle. Debris is kept out of the telescoping assemblies by use of wipers while damping and lubrication fluid is contained within the telescoping assemblies by use of oil seals. These wipers and seals are fixed to the upper end of the sliders. A spring and damper system are contained within the telescoping assemblies to create a system that provides the benefits of better handling and control. The oil seal system allows for a variety of spring damper designs to be utilized within the telescoping assemblies. However, when a suspension fork of this design is loaded torsionally, which happens during steering and when hitting bumps at an angle, the sliders can rotate relative to the stanchions due to the round cross section's inability to resist torsional loads. With round tubes the only torque that can be transferred from the slider to the stanchion is the amount developed through friction between the fork bushings and the tubes they support. This interface is made to be very slippery so that motion from terrain irregularities can be easily accommodated. The amount of torque transmission then is negligible. This torsional rotation results in increased perceived fork flex and can cause a lack of control due to the imprecise feeling to the rider.
A less common approach to a telescopic front suspension system uses non-round tubes for the telescoping assembly to create the ability to transfer torque from one tube to the other. One such design utilizes an inner tube with a plurality of flats making up its outside shape. An outer tube is positioned coaxially and telescopically to the inner tube and has a corresponding number of flats making up its inside shape. The flats communicate with one another via cylindrical needle bearings, which roll on the flats when the inner and outer tubes are moved relative to one another. A system like this can transmit torque as well as telescope. However, due to the flat sections on the outside of the inner tube a typical oil seal and wiper arrangement cannot be used. This system uses a flexible bellows to keep debris from entering the telescoping assembly. The bellows can tear and is not watertight so contamination is a common problem with a system like  this. Also, since oil can not be sealed well by this bellows, only a self contained cartridge damper system can be utilized within this system, which limits the its performance potential.
Other approaches to the torque transferring telescoping assembly have been to employ grooves on the inside diameter of the outer tube with corresponding grooves on the outside diameter of the inner tube. The grooves in this case communicate via loose balls bearings.
Additionally there are linkage type systems, which provide a scissor linkage similar to the landing gear of an airplane. One end of the linkage is connected to the outer tube. The other end of the linkage is connected to the inner tube. The linkage can fold when the suspension goes through its travel but it does not allow the inner and outer tube to rotate relative to one another.
All of these torque-transferring telescoping suspension systems contain more parts and are more expensive to produce than the bushing style round tube system described above.